---
title: Random
slug: /random
section: Math
---

## Random

You can instantiate the [[Random]] class with an optional seed number. You can
reuse this seed anytime to get the exact sequence of random numbers back. If no
seed is provided, it uses a static base seed from `Date.now()` ticks and increments each call.

If you create mulitple instances of `new ex.Random()`, it will sequentially increment a base seed from an initial `Date.now()` call.  So each instance of the generator will be unique.

```ts
const rand = new ex.Random(1234)

// random integer between [min, max]
rand.integer(0, 10)

// random floating number between [min, max]
rand.floating(0, 10)

// random true or false
rand.bool()
// random true or false with 40% likelihood of being true
rand.bool(0.4)

// next floating point between [0, 1]
rand.next()

// next integer between 0 and Number.MAX_SAFE_INTEGER
rand.nextInt()

// pick a random element from an array
rand.pickOne([0, 1, 4, 10])

// pick a 2 random elements from an array
rand.pickSet([0, 1, 4, 10], 2)
// pick a 4 random elements from an array, allowing duplicates
rand.pickSet([0, 1, 4, 10], 4, true)

// generate an array of 9 random numbers between [min, max]
rand.range(9, 0, 10)

// randomly shuffle an array using Fisher/Yates algorithm
rand.shuffle([0, 1, 2, 3, 4])

// Multi-sided dice helpers
rand.d4()
rand.d6()
rand.d8()
rand.d10()
rand.d12()
rand.d20()
```

A seeded random is very useful in games to do things like terrain generation, procedural
content generation, etc. It allows you easily debug your algorithms by reusing
the same seed, as well as to ensure your algorithms are deterministic.
